diff --git a/tests/phpunit/includes/bootstrap.php b/tests/phpunit/includes/bootstrap.php
index 7e97dd55bc2b7..60911bc362ff4 100644
--- a/tests/phpunit/includes/bootstrap.php
+++ b/tests/phpunit/includes/bootstrap.php
@@ -250,10 +250,17 @@
 define( 'REST_TESTS_IMPOSSIBLY_HIGH_NUMBER', 99999999 );
 
 /*
+ * Isolate uploads in a dedicated directory when running the core test suite only,
+ * so that plugins and themes using the test suite keep the default uploads location.
+ *
  * Tests that cover the upload_path and upload_url_path options run in a separate process
  * with WP_TESTS_SKIP_UPLOADS_CONSTANT set, as UPLOADS overrides those options.
  */
-if ( ! defined( 'UPLOADS' ) && '1' !== getenv( 'WP_TESTS_SKIP_UPLOADS_CONSTANT' ) ) {
+if (
+	defined( 'WP_RUN_CORE_TESTS' ) && WP_RUN_CORE_TESTS
+	&& ! defined( 'UPLOADS' )
+	&& '1' !== getenv( 'WP_TESTS_SKIP_UPLOADS_CONSTANT' )
+) {
 	define( 'UPLOADS', 'wp-content/test-suite-uploads' );
 
 	/*
diff --git a/tests/phpunit/includes/functions.php b/tests/phpunit/includes/functions.php
index cc39bbc52a62d..a3c86e60aefa3 100644
--- a/tests/phpunit/includes/functions.php
+++ b/tests/phpunit/includes/functions.php
@@ -360,7 +360,9 @@ function _upload_dir_https( $uploads ) {
  * @return string The upload URL.
  */
 function _upload_get_url( $path = '', $scheme = 'http' ) {
-	return $scheme . '://' . WP_TESTS_DOMAIN . '/' . trailingslashit( UPLOADS ) . ltrim( $path, '/' );
+	$uploads = defined( 'UPLOADS' ) ? UPLOADS : 'wp-content/uploads';
+
+	return $scheme . '://' . WP_TESTS_DOMAIN . '/' . trailingslashit( $uploads ) . ltrim( $path, '/' );
 }
 
 /**